Intermodal cargo containers (also referred to as freight or shipping containers) are reusable transport and storage units for moving products and raw materials between locations, including between countries. Intermodal cargo containers are standardized to facilitate intermodal transport such as among marine transport, freight train transport, and freight truck transport. Standardization of cargo containers also is referred to as containerization.
Containerization has provided global commerce with many benefits. Shipped goods move more easily and cheaply. Manufacturers know that goods loaded at one location can be readily unloaded at the destination. Cargo security has been improved, as containers are usually sealed and can be locked to discourage tampering and theft. Containers also have a longer service life, and there is a stronger market for used containers. Additionally, the costs of cargo containers themselves is lowered because a manufacturer can make these in larger volume knowing that potential customers are available all over the world.
Several international standards have been created to promote international containerization. For instance, the International Organization for Standardization (ISO) has promulgated applicable standards including R-668 to define terminology, dimensions, and ratings; R-790 to define identification markings; R-1161 to recommend corner fittings; and R-1897 to set forth dimensions for general purpose containers. Other standards include ASTM D5728-00, ISO 9897 (1997); ISO 14829 (2002); ISO 17363 (2007); ISO/PAS 17712 (2006); ISO 18185 (2007); and ISO/TS 10891 (2009). An international specification for coating/paint performance is provided by IICL (Institute of International Container Lessors). See also International Organization for Standardization (ISO), Freight Containers, Vol. 34 of ISO Standards Handbook, 4th Ed., 2006, ISBN 92-67-10426-8; and Levinson, Marc, The Box: How the Shipping Container Made the World Smaller and the World Economy Bigger, Princeton, N.J., Princeton University Press, 2006, ISBN 0691123241. Each of these standards and publications is incorporated herein in its entirety for all purposes.
Cargo containers experience harsh, corrosive environments during their service life. When shipped by sea, the containers are exposed to the corrosive effects of salt water. When exposed to nature, the containers must withstand wind, sun, hail, rain, sand, heat, and the like. Containers exposed to the sun can bake to temperatures of 82° C. (180° F.) or even higher.
Accordingly, cargo containers must be made in a way that allows the containers to survive this exposure for a reasonable service life. As one strategy, containers can be made from corrosion resistant materials such as stainless steel, weather steel (also known as weathering steel, COR-TEN brand steel, or CORTEN brand steel). Even when made from such corrosion resistant materials, it still generally is desirable to further apply durable, abrasion resistant, corrosion resistant coatings on the containers as further protection against degradation. Coatings also may be used for decorative, informative, or brand identity reasons.
A typical coating strategy involves applying a top coating over a primer coating. Often, the coatings are applied to one or more vertical surfaces. Historically, mostly solvent-based coating systems have been used to protect cargo containers as many proposed water-based systems have been unable to satisfy the applicable performance demands and/or standards. In particular, waterborne coatings are difficult to apply in widely varying humidity conditions, as an applied film of the coating stays wet for a longer period of time and/or does not dry uniformly, resulting in increased sag of the coating if the viscosity does not recover within the drying period. Consequently, only solvent-based coating systems have found widespread commercial acceptance in the industry. The container industry retains a strong bias against using water-based coating systems.
With increased environmental awareness, there is a strong desire to develop improved technology that would allow use of water-based coating systems to protect cargo containers or other substrates (e.g., vehicles such as rail cars or trucks).